


Enemies Within (Ben Tennyson x Reader)

by Natsugirl48



Category: Ben 10 Series
Genre: Ben is turned on by it, Everyone is older, F/M, I Wrote This Instead of Sleeping, Other, Reader is a bad ass, Rook is a precious child, Sorry Not Sorry, There will be shameless smut, no regrets tho
Language: English
Status: In-Progress
Published: 2020-04-16
Updated: 2020-04-19
Packaged: 2021-03-01 22:47:38
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 4,308
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/23674870
Author URL: https://archiveofourown.org/users/Natsugirl48/pseuds/Natsugirl48
Summary: There's a new enemy, one stronger, and older than the galaxy itself. So who better to stop him than THE Ben Tennyson?(Y/n) (L/n)! That's who. She's a bad-ass plumber, who's definitely beating Ben at his own game, when it comes to catching bad aliens.Ben Tennyson x ReaderBoth are 18 in this.
Relationships: Ben Tennyson/Reader
Comments: 5
Kudos: 30





	1. New Mission

**Author's Note:**

> So, this follows no omniverse story line, the bad guys are new.
> 
> Gwen and Kevin are currently living somewhere together and will not make many if any appearances.  
> Rook is still partnered with Ben.   
> Ben is single (you'll hear about that later) and 18.  
> The bad guy is based off of Lovecraft's monsters, but it's purely for appearance and motive.
> 
> My goal is to make this book fun and different, but also if you don't remember, or didn't finish omniverse, there's no spoilers or restrictions. There may be a lemon...idk yet, it'll of course be an optional read if I do write it in. I really hope y'all enjoy this read. :)

You had just defeated some rogue Lenopans or sludgepuppies as most plumbers called them when your phone started to ring. You take a deep breathe and answer it. 

"(Y/n) responding."

"(Y/n), this is Max Tennyson, I'm requesting your presence at the academy. You will be teleported her in a few minutes, so see to it that you're in proper attire." 

"Do I get a choice?" Your answer was the line being hung up. You sigh and make your way to your hoverboard. It's been a while since you've been at the academy. The floor beneath begins to turn blue as you feel your body go numb. You close your eyes on reflex. When you opened them you saw you were at the academy. You felt eyes on you as you moved forward to the top floor. The loud whispers of the rookies and young cadets didn't go unnoticed by you.

"Isn't that...?"

"Why is she here?"

You could feel the fear of the students who knew of you. It caused you to smirk with pride. You were about to make your way to the elevator that goes to the top floor when someone stepped in your way. 

You look up to see a female tetramand. She was young so her body wasn't as big but she still had a lot of height on you. You put your hand on your waist, ready pull out your mechanical staff. The tetramand leaned a little forward to be at your eye level. 

"You're (Y/n) (L/n) right?" She said seriously. 

"Who's asking?" You say, getting into a fighting stance slowly. 

"Well I am!" The tetramand stood up straight and smiled brightly at you. "I heard all the rumors about you. It's a real pleasure to meet you. She stuck out one of her four arms towards you. With a relieved smile you shook her one of her hands. 

"It's always nice to meet the rookies. But if you'll excuse me I have to meet the Earth Magister." The tetramand nodded her head with excitement and stepped off to the side. You enter the elevator and sigh as soon as the door closes.  
It was a short and fast trip to the top floor. You thank your rebellious childhood that made trips to the Magister's frequent enough that you could find your way blindfolded. You were about to knock on the door when it opened automatically. 

You see the great Max Tennyson, sitting behind a desk. He had papers, upon papers on its surface and a stressful look. You sit in on of the chairs in front of his desk and smile. 

"Need some help sir?"

Max looked up from the papers and smiled as soon as he saw you. "(Y/n)!" Quickly getting up and walking around the desk, the older gentleman pulled you into a soft hug. "Thank you for coming." You part and cross your arms with a playful grin on your lips.

"You didn't give me the choice not too."

Max laughed. "That is true." The laughter and light atmosphere soon ceased when Max looked at you seriously. "Sadly, I didn't call you here for some laughs and a friendly reunion." Max takes something out of one of the drawers of his desk and tosses it at you. You catch it with ease and instantly feel the color of your face drain.

"You've got to be kidding me."

"I'm afraid not. This is a-"

"It's a map of the planet Azamoth," you finish for him. You look at the small cube and push the small button on the side with your thumb. It opened up a small projected map of the planet. "A map with a tracker for one of the worst aliens in the galaxy. Lathotep." You close the map and look back at Max. 

"This is your next mission. You will be given enough money to stay on the planet for a few months. This mission is going to be recon for now."

"Recon? You're sending me to this planet and expect me not to-"

"I expect you to follow orders." You instantly shut your mouth and turn your gaze to the ground below you. Max sighed and placed a hand on your shoulder.  
"I know what this means to you, but I need you to keep your eyes on the mission okay? 

You nod your head agreement. "Yes sir." You place the map in your small bag on your waist opposite to your mechanical staff.

"Ben and Rook will be accompanying you on this mission." Your eyes widened at his statement.

"With all due respect, I don't think that's the greatest idea." 

Max took a seat behind his desk and folded his hands. "I understand your concern. But the omnitrix will be a great ally to you on this mission."

"The omnitrix yes, but not it's bearer. Who is notorious for being impulsive, cocky, and arrogant." You cross your arms and put all your weight on one leg. "Besides that point, you'll be sending the most powerful weapon in the galaxy straight to the enemy."

"Ben along with you are both 18 now. Though you're right about his personality, his time with the omnitrix and in battle makes him more than qualified for this mission." Max then gave you a gently smile. "It would also be nice to see you acquainted with more people your age. " 

You sigh. "Sir..." You were about to express more concerns when Max shook his head. 

"You're dismissed (Y/n), please head down to the Transportation chambers to meet your temporary partners and start your mission."

With a quick nod, you turn on your heel and head down to the chamber.

With Ben and Rook

"I vote we leave without her." Ben said with a groan. "It should not take this long to be debriefed for a mission."

"Actually, this a proper amount of time to be debriefed, you just never pay attention." Rook said with his monotone voice. 

"Oh well, who is this chick anyways that she has to make THE Ben Tennyson wait?"

Rook looked at Ben with disbelief. "You don't know who (Y/n) (L/n) is?"

"No and why should I." Ben said crossing his arms. "She's probably some uptight, by the book, old lady, who's going to be need to be saved by me when she messes up this mission." Once he finished his rant Ben looked around for his partner. "Uh Rook?" 

He turned around to see a girl slightly smaller than him, with her arms crossed and a resting bitch face that could kill. Rook standing next to her. "Uptight old lady huh? That's a new one."

You walk right past him and onto the ship, for your mission. Ben gave Rook a look and the Revonnahgander just shook his head and boarded after you. Ben sighed and followed suit.

"This is going to be a long mission."


	2. Meet Your Partners

**Summary for the Chapter:**

> Ben get's his ass handed to him.

**Notes for the Chapter:**

> So, this follows no omniverse story line, the bad guys are new.
> 
> Gwen and Kevin are currently living somewhere together and will not make many if any appearances.  
> Rook is still partnered with Ben.  
> Ben is single (you'll hear about that later) and 18.  
> The bad guy is based off of Lovecraft's monsters, but it's purely for appearance and motive.
> 
> My goal is to make this book fun and different, but also if you don't remember, or didn't finish omniverse, there's no spoilers or restrictions. There may be a lemon...idk yet, it'll of course be an optional read if I do write it in. I really hope y'all enjoy this read. :)

The ship wasn't too big, but it wasn't small either. It was built for journey's such as this one. It had a training room, kitchen, 2 bedrooms, and 1 bathroom. It was a small apartment meant for space travel. You walk to the very front of the ship, to the control panels. You sit down and take out the map Max gave you. Connecting it to the ship's main control you felt the ship jolt awake. A robotic male voice spoke loudly throughout the spacecraft. 

"Hello, I am Marlowe, your automatic piloting guidance assistance. Is Azamoth your correct destination?"

"Yes."

"Route provided by Sector Map, will take about 10 days and 12 hours."

"What?" You sigh and shake your head. "Yes, please proceed." The ship whirred and you felt it lift off the platform and zoom out of the academy's Transportation chamber. You get up out of the chair and head over to check out your room. The door opened automatically for you. Upon walking in the room you saw a light purple scan pass over you. When the door closed you turned around to see a holographic panel with your name appear. There was a red x and a green check mark under it. You smile and click the green check mark.  
You heard panels open and see a bed and closet appear.

"That's cool." The bed was placed on the left wall, a small chest for trinkets or items next to the door, and a closet across the bed. You walk over to the closet and see some shirts and outfits that were your size. "Thanks for the clothes, Marlowe." 

You take out one of the outfits and put it on. Black pants with a light gray shirt. You snap on your tan waist bag and your mechanical staff. You exit your room and head down to the training room. You see Ben that was already in there, fooling around with the training holograms. You watched as he practiced shooting crystals as diamond head, then once the omnitrix timed out, he continued to evade the holograms attacks until he could transform again; this time as four arms. 

It didn't take you long to realize that he was trying to show off his skill. He must've noticed you watching when the omnitrix timed out. You roll your eyes when you see him wink while lifting the hologram. He slammed down the hologram, causing it to disappear. Ben changed back into his normal form and walked over to you. He ran a hand through his hair and gave you a smug grin. 

"Impressed?"

You rolled your eyes and crossed your arms. "Hardly, you used the most basic setting of the hologram."

Ben looked at you dumbfounded. "Say what now?"

You sigh and walk to the middle of the room. "Marlowe." The training room glowed a light blue. "Looma Red Wind" You step back a little and watch as a perfect holographic copy of the female tetramand appeared in front of you.

Turning to face Ben, it was your turn to look smug. "The ship is connected to the Plumbers database, so it has information on everyone of your enemies old and new." A screen above you and Looma appeared with a 3 second countdown. As soon as the screen said go, the tetramand charged at you. You easily flipped over her, using your staff to push off the ground. Causing the hologram to bump into the wall. You twirl you staff and get ready for another charge. 

The next time she charged, the hologram had the hammer equipped. You smirk, holograms were always predictable. The hologram came out you fast ready to smash you with her hammer, but as fast as she came was how fast she fell. Before she had the chance you extended your staff to hit her jaw. For the finishing blow you jumped and hit the tetramand with a back flip kick. You smiled satisfied at the time it took you to take her down. 1.43 new record. 

You twirled your staff in one hand before collapsing it and putting it back on your waist. Facing the boy you walk over to him. "Holograms are all made with a certain specificity. The enemy you chose is what skill you're trying to improve on."

Ben crossed his arms. "Is that why you chose an easy enemy?"

You scoff at his comment. "Oh? Then which enemy matches your standard of difficult?" Ben smirked and walked to the middle of the room. 

"What was the name?" Ben said putting his hand on his chin. "Oh right.Marlowe! Display countdown." Ben looks at you, and you suddenly realize what he was implying.  
This should be fun. You walk towards him and see the countdown start. You got into a fighting stance.

"To be clear, I'm gonna take it ea-" Ben's sentence was cut off by you delivering a right hook to his face. He stumbled back a little and held his cheek. "HEY!"

You pointed at the display of the timer that starts when a match begins. Ben shakes it off and charges at you. You easily evade him. Putting both hands behind your back, you stick out a leg. Turning on your heel, you trip Ben, causing him to land on his stomach. Seeing him on the ground in less than 45 seconds, you held your mouth, trying to contain your laughter. 

"I'm sorry you were going easy on me?" You laughter ceased when felt something sweep under your feet causing you to fall. 

"Pinned ya." Ben had both your wrists pinned to the ground by your head and one of his legs between yours. You felt your face flush because of how close he was to you. Not wanting to lose this battle, you swiftly kick him in the shin, and push him off of you. Placing both of your legs on his arms, you had successfully prevented him from moving.

"I win." You said with a victorious smile. Ben tried to move his arms but to no avail, he was trapped.

You were snapped out of your moment when you heard clapping. Both you and Ben turned to see the revonnahgander standing at the entrance. Embarrassed at the sudden audience you get off Ben. You walk over to him and offer your hand. 

"So you must be Rook. I apologize for not introducing myself earlier." You said with a smile. Rook took your hand and offered his own introduction. 

"I am Rook Blonko. It is a pleasure to make your acquaintance ma'am." You blush at the formality. 

"There's no need for formalities, please just call me (Y/n)." Rook nods with a smile. "So, I take it you watched me wipe the floor with your partner?" You say pointing behind you at Ben.

"You didn't wipe the floor with me." Both you and Rook turned your gaze to the boy, who was walking over. " I told you, I was going easy on you!"

"Got it, well next time" You turned to face him. "You. Might. Win." With every word you gave him a gently tap on the nose. With a teasing smile you turn on your heel and you wave a goodbye to the two boys. "I look forward to working with you two."


	3. Alone Time In the Kitchen

**Summary for the Chapter:**

> Ben can't sleep, but the night didn't turn out as he thought it would.

**Notes for the Chapter:**

> So, this follows no omniverse story line, the bad guys are new.
> 
> Gwen and Kevin are currently living somewhere together and will not make many if any appearances.  
> Rook is still partnered with Ben.  
> Ben is single (you'll hear about that later) and 18.  
> The bad guy is based off of Lovecraft's monsters, but it's purely for appearance and motive.
> 
> My goal is to make this book fun and different, but also if you don't remember, or didn't finish omniverse, there's no spoilers or restrictions. There may be a lemon...idk yet, it'll of course be an optional read if I do write it in. I really hope y'all enjoy this read. :)
> 
> https://img.youtube.com/vi/A0T6LwpJGxw/0.jpg this is the song used in the chapter and what I wrote it too.

Ben and Rook were both in their shared room. They had a bunk bed, a desk, 2 closets, and a shared chest. Ben was on the top bunk sulking, while Rook was reading at the desk. 

"How come she gets her own room?" Ben said while crossing his arms.

Rook turned around in his seat and looked at his partner with confusion. "Would you like to share a room with (Y/n)?"

Ben's face turned a light shade of pink. "T-that's not what I meant!" Rooks face looked at him with more confusion. "Forget I said anything." With that Ben laid down on his bed, facing the ceiling. "So, what's so special about her anyways?"

Rook's sudden chuckle caused Ben to sit up. "What's so funny?"

"Even though you seem to dislike Miss (Y/n), you are still very much intrigued by her."

Ben rolled his eyes and scoffed. "I'm not 'intrigued' by her," he said using air quotes. "I just want to know why she's so-" Ben was cut off by Marlowe's voice, booming throughout the ship.

"Please come to the kitchen area. Dinner is ready."

Ben slid off the top bunk and followed Rook out of the room to the kitchen. There was a little counter top with 4 seats and a what looked like an oven in front of it. The two took their seats and waited. The oven then opened and revealed chili fries on a tray with steamed tofu on another. A long platform was extended from the oven to the counter where the two boys sat. 

Ben grabbed the chili fries tray, Rook taking the other one. The platform rotated back and revealed another tray coming out of the oven. This time with two glasses of water. Once everything was off the platform it went back into the oven.

"Cool." Ben said right before he gorged himself in his meal. Rook glanced at Ben, before looking at the empty seats that surrounded him. 

"Uh..Marlowe? Where is (Y/n)?"

"Miss (L/n) will not be joining us for dinner." Marlowe said throughout the kitchen.

"How come?" Rook said with a hint of sadness in his tone.

"Miss (L/n) is currently in the training room." 

"Of course she is.." Ben said underneath is breath.

It had been 4 days since Ben had talked or even seen you. You were either locked in your room or in the training room.  
It was about 2 in the morning or at least that's what Marlowe said, since there's no time in space. Ben laid in his bed bored out of his mind. This was going to be a sleepless night for him. Ben got out of bed and was making his way to the kitchen when he heard music. It was coming from the training room.

"Is she really up right now?" Ben changed his objective and made his way to the training room. The music got louder as he neared the room. He saw that you were standing in the middle of the room as holographic drones shot lasers at you. You dodged the lasers easily while humming along to the music. Using a beam gun, you took out every single one of the drones. 

You looked at the gun and dropped it on the ground. You were breathing heavily, running a hand through your hair you smiled. "Revenge and a little bit more." You sang to yourself quietly. You were about to leave when a drone that was hiding shot at your leg while you were turned around. Your weight began to collapse under you. Not wanting to crash on the ground, you roll into the fall, took out your mechanical staff and threw it at the drone. This successfully put an end to the training session and music. 

"Are you okay?" The voice surprised you at first, but you looked up from your leg to see Ben with concern on his face. You cock your head to the side.

"Y-yeah." You push yourself off the ground. That was a mistake. Your body was fatigued and in pain, sudden movements was not going to work. You prepared to hit the floor when you felt an arms around you. Ben had one hand on your shoulder and the other on your waist. Against your will, you felt your face heat up. Ben chuckled at your flustered expression. You gently try and pull yourself away from the boy. 

"Let me help you." 

"N-no, I can do it." 

Ben sighed. "It's fine, let me help." With a lot of complaints, Ben helped you walk to the kitchen. He placed you on one of the chairs. "Okay stay here, I'm gonna find a first aid kit."

You rolled your eyes. "Marlowe, FA288." The oven opened and revealed a burn bruise bandage. Created specifically for wounds made by drone lazers. You smile and take the bandages. "Thank you Marlowe."

A stifled laugh turned your gaze back to the omnitrix bearer. "Care to repeat the joke?" You say with slight annoyance.

"You just thanked the ship. Appreciation and gratitude phrases aren't in it's programming." 

You shrug your shoulders in response. Getting up from your seat you begin to struggle to exit the kitchen. Ben moved in front of you and forced you to sit back down. You looked at him with confusion. 

"I told you to let me help you!"

You looked at your wound and then back up to him. A playful smirk made its way on your lips. "Are you sure? You don't seem practiced in stripping women's clothes off."

Ben answered without processing the question "Of course I'm sure. It's not that hard to- uh..." His face turned a bight red. You giggle at his expression. "So you are capable of emotion?" Ben said with surprise. His face still a little pink.

"I wouldn't say I'm deprived of it. 

"That's a relief." Ben said with a smile. "Now all we have to worry about is when this Lathoteppy guy tries to steal the omnitrix and take over the world." 

You smile ceased when you heard what Ben said. "Excuse me?" Disbelief dripping in your tone.

"What? Every mission I'm sent on has a bad guy wanting the omnitrix. They all want it so they can use it for world domination and yada yada. I choose not to worry about it since I have saved the world more than a hundred times by now." 

"And your plan was to just confront him with the omnitrix, defeat him, and put him behind bars or send him to the null void then?"

"Exactly! My mission is over and we can all go home."

You felt anger boiling in you because of the incompetence he had. "Well you certainly had me fooled."

"What do you mean?"

You winced as you got up again. You took a small step towards Ben. "I was starting to think you were a decent guy." You placed an accusing finger on his chest. "Turns out you're just a cocky, arrogant, narcissistic prick. Lathotep doesn't need the omnitrix for world domination and if you had listened to the debrief or did some research you'd know that."

You huffed and turned on your heel, heading for your room. It hurt to walk on your own but you couldn't stand to be near him at the moment. Before you exited the kitchen you paused but didn't turn around. "And by the way this mission is not yours."


	4. A Little History Lesson

**Summary for the Chapter:**

> This is hopefully going to be the only "short" chapter.

**Notes for the Chapter:**

> So, this follows no omniverse story line, the bad guys are new.
> 
> Gwen and Kevin are currently living somewhere together and will not make many if any appearances.  
> Rook is still partnered with Ben.  
> Ben is single (you'll hear about that later) and 18.  
> The bad guy is based off of Lovecraft's monsters, but it's purely for appearance and motive.
> 
> My goal is to make this book fun and different, but also if you don't remember, or didn't finish omniverse, there's no spoilers or restrictions. There may be a lemon...idk yet, it'll of course be an optional read if I do write it in. I really hope y'all enjoy this read. :)

It had been another 3 days since you stormed off in anger at Ben's declaration. He didn't understand why you were so angry, what he said was true...well most of it. Ben didn't realize it but he had just sighed for the 5th time within the last 30 minutes. Rook looked behind him at the confused teen laying on his top bunk.

"Is something wrong Ben?" Rook asked with genuine concern. "Are you feeling ill?" Ben didn't respond. "Does it have to do with Miss (Y/n)?" Ben slowly sat up and turned to the slightly older alien.

"I just don't get it? Why is she so...so DIFFICULT?" 

Rook cocked his head to the side in confusion. "You still have not figured out who Miss (Y/n) is?"

"No I haven't Rook! So just fill me in already!" Ben yelled slightly angry at the situation, though the poor alien was the one he was taking out his pent up frustration. Rook nodded his head and began his history lesson. 

Gemini was one of the best plumbers ever known. She was resourceful, powerful, and courageous. She had everything any normal plumber would want. Yet, she was unsatisfied. More than anything she ever wanted, Gemini wanted to be a mother. But, that was impossible for her, her body couldn't reproduce. 

While on a mission Gemini was sent to Azamoth to track down a criminal. After apprehending the criminal she sent a message to the plumbers saying that was retiring early. The reason being was that she was in love with a man named Lathotep. He was a Lovecraftian; one of most dangerous breeds of aliens. However it didn't matter, Lathotep promised Gemini the one thing she wanted. Children, a legacy. 

Lathotep created 5 children for her using his and her DNA along with a lot of Lovecraftian science. Gemini loved each and every child so much. She spent all her time with them, cherishing and treasuring them. Lathotep grew jealous of this love. He created these children for her so that she would love him more. 

He grew mad with jealousy and began plotting the downfall of his own children. When Gemini took her middle and second eldest child out, Lathotep killed the youngest two children. He then went on to kill the eldest. When Gemini came back to the bloodshed, she told the last two children she had to run and hide. 

The second eldest hid the middle child in a cabinet crying and alone while they left to go find Gemini. Instead all they found was an insane father crying while stabbing their mother. The child ran to go find their sibling, but Lathotep got to them first. The middle child stayed in the cabinet until Lathotep found her. 

He was going to kill her, when she jumped at him with a knife, ready to fight for her own life. Lathotep surprised and astonished, kept this daughter alive. He trained her, made her bloodthirsty and made her into a monster.

She was 6 when the plumbers finally captured her and took her. Because of her origins and how many things she had done, she was raised by the many plumbers and trained. When she was 8, she was accompanying the greats on missions, by the time she was 12 she was doing her own minor missions. And now she is -

"(Y/n)" Ben said interrupting Rook's dramatic ending to the story. Ben quickly hopped off his bed and made his way to your room door. He knocked a few times before it slid open. You were in pj's, your hair was slightly disheveled, and you had a resting bitch face on. You were about to speak but Ben beat you to it.

"I'm sorry." You raised an eyebrow. This was new. "I shouldn't have said those things in the kitchen and I shouldn't have acted the way I did." Ben was looking down to the ground with his hair covering his face. Ben looked up when he saw a hand outstretched to him 

"Friends?" You said with a small smile.

Ben nodded with agreement. "Friends."


End file.
